The options for level are 0 (off), 1 (queries > 100ms), and 2 (all queries).
If you would like to profile queries that take longer than another time
period, use the database command and pass it a second option, the number of
milliseconds. For example, to profile all queries that take longer than one
second, run:

<?php

$result = $this->command(array('profile' => 1, 'slowms' => 1000));

?>

Profiled queries will appear in the system.profile
collection of this database.